1. Field of the Invention (Technical Field)
The present invention relates to a method and apparatus for creating pre-stressed zones in concrete through the introduction of a chemical while the concrete is in a liquid stage.
2. Description of Related Art
After a slab of concrete has been poured, one or more pre-stressed zones are then created in the slab. These pre-stressed zones act to guide cracks along straight and predetermined pathways. Typically, such pre-stressed zones are created by cutting through an upper portion of the concrete with a circular saw that is made to travel in a relatively straight line across the slab. Use of such a saw, therefore, requires that the concrete first be allowed to harden. Hardened concrete is quite abrasive and thus typically requires a diamond coated cutting blade with a constant flow of water applied thereto. This process is both slow and expensive. There is thus a present need for a method and apparatus for installing pre-stressed zones in concrete in a fast and inexpensive manner.
The present invention is directed to a method for creating a pre-stressed zone in wet concrete which includes providing wet concrete, providing a chemical capable of retarding, delaying, or inhibiting the setting of wet concrete, physically penetrating a top surface of the wet concrete, placing the chemical below the top surface of the wet concrete, and allowing the wet concrete to set.
In the method, penetrating a top surface can include rolling a substantially circular blade at least partially through a portion of the wet concrete, as well as pressing a blade at least partially into a portion of wet concrete. The chemical can be sprayed into an opening in the wet concrete, or the chemical can be sprayed onto a blade that is subsequently placed at least partially into the wet concrete. The chemical used in the present invention can also be saturated into a rope which is then at least partially disposed beneath a surface of the concrete.
Regardless of how the chemical is added to the wet concrete, after the chemical has been added, the surface of the wet concrete can optionally be smoothed.
The chemical used in the present invention preferably contains a hydrocarbon solvent and more preferably contains aromatic 100 and/or mineral spirits. Desirable results can also be obtained when sugar-water is used.
The apparatus of the present invention also includes introducing a chemical below a top surface of wet concrete. This apparatus preferably comprises a roller with a blade that is disposed at least partially around an outer surface of the roller, an axle fixedly or rotatably secured to the roller and substantially axially aligned therewith, one or more handles fixedly or rotatably connected to the roller, and a chemical application system which applies a chemical to the blade.
The blade can have a plurality of orifices disposed radially therethrough, and through which the chemical is excreted. Or, the chemical can be applied to the blade with a spraying system.
A pump can be coupled to the roller such that when the roller is rotated, a volume of chemical is pumped which is proportional to the amount of rotation experienced by the roller. A plurality of pistons can be radially disposed within the roller. A cam-shaped member can be attached to an axle thereof such that rotation of the roller causes the cam-shaped member to reciprocate the pistons, thus pumping the chemical.
One or more chemical-distributing wipers can be provided which spread chemical across the blade. Further, one or more wet concrete scrapers can be provided which help to remove wet concrete that sticks to the blade.
The apparatus can be powered by a mechanism, including but not limited to one or more electric motors, gas motors, pneumatic motors, hydraulic motors, combinations of these, etc. The power mechanism can be directly coupled to the apparatus, or a drive mechanism can be provided which transfers power from the power mechanism to the roller or the axle. The power mechanism can be disposed internal of or external to the roller.
The present invention also relates to an apparatus for introducing a chemical below a top surface of wet concrete which includes at least one propulsion member; a power source having an internal power source, an external power source, and/or combinations thereof; a movably positional blade; and a chemical application system.
The apparatus can also have one or more guide mechanisms. The guide mechanism can be one or more tracks, a string guide, and/or a laser guide.
One or more vibrators can also be provided, and the propulsion member can include at least one rotatable leg member and/or at least one wheel. The chemical application system can apply a chemical onto a surface of the blade, and/or apply the chemical directly into a depression of the wet concrete.
An automated controlling mechanism can be provided, which can optionally include a microcontroller.
The present invention also relates to a method for creating a pre-stress zone in wet concrete which includes providing a rope saturated with a chemical, disposing the rope at least partially within wet concrete, and allowing the wet concrete to set. The apparatus can include a rope holder, and the rope holder can have a spool and/or a spool holder.
Disposing the rope at least partially within the wet concrete can include disposing the rope at least partially around a circumference of a substantially circular rotatable blade. Optionally, after disposing the rope within the wet concrete, the wet concrete can be smoothed.
The present invention also relates to an apparatus for inserting a chemical-saturated rope below a top surface of wet concrete which includes a roller, an axle at least substantially axially aligned with the roller, at least one handle, and a blade circumferentially disposed around the roller. The blade can include a channel, a groove, an indentation, or a trough.